#include <stdio.h>
union Data{
    int num1;
    char num2;
    short num3;
};
int main(void)
{
    union Data data;

    data.num1=66;
    data.num2='a';
    data.num3=99;
    printf("sizeof(data):%ld\n",sizeof(data));
    printf("data:%d\n",data.num1);//取最后一个复制的，前两个被覆盖
    return 0;
}